The invention relates to a private part irrigation system for use in the urinal, for example.
A conventional system of this kind is constructed such that water from a suitable supply is fed to a heated water tank having a heating unit disposed therein which is intermittently controlled to heat the water to a desired temperature for subsequent irrigation or ejection use. However, it will be noted that for a body of water encompassing a substantial height, the water temperature will be high in the upper region while it is low in the lower region, and there is a temperature differential also in the lateral direction depending on the arrangement of the heating unit. As a consequence, the water which is sprayed to the private parts of a human body has a varying temperature, causing discomfort to the user.
In the conventional system, there is provided a control thermostat unit which is disposed in the water contained in the tank to sense a change in a temperature thereof and which intermittently controls the connection of the heating unit with a power source therefor. In this manner, the water temperature is controlled to a level which is established by the thermostat unit. However, as mentioned previously, the water temperature has a varying value in the upper and lower regions of the tank and depending on the disposition of the heating unit. The thermostat unit is often disposed in the upper region of the body of water contained in the tank while the discharge port communicating with the ejection passage is formed in the lower region. Since the heated water is to be ejected toward a human body, there must be an upper limit preset on the water temperature in order to avoid a critical damage to the human body such as scalding. It will be understood that the upper limit temperature will be that of the water contained in the upper region while the water in the middle and lower regions will be at a temperature which is substantially reduced than the optimum temperature. Such temperature differential also results in providing a discomfort when the water is ejected toward the human body.
Since the water temperature increases with an increasing elevation, it is necessary for the thermostat unit to detect the water temperature as close to the water level as possible. However, in practice, the temperature sensor of the thermostat unit is arranged to extend from the water level to the middle region in order to assure a reliable detection, with result that the sensor detects a mean temperature over the body of water which extends from the middle region to the water level. This prevents an accurate detection of the maximum water temperature, making it difficult to preset a temperature value at which the thermostat unit is to be operated. Specifically, the operating point for the thermostat unit must be determined from an approximate evaluation of the temperature differential from the upper limit value. Also, the mean water temperature must be predicted when evaluating the temperature differential. It is very difficult to satisfy these requirements, rendering it virtually impossible to achieve an optimum temperature control of the water. It will be evident that such drawbacks will be even more aggraviated when the thermostat unit is located in the lower region.
A conventional system also includes a safety or high limit thermostat unit, in addition to the control thermostat unit, which is operative in the event of a failure of the control unit. The safety or high limit thermostat unit has an operating point which is established at a higher level than that of the control thermostat unit. However, the establishment of the operating point of the safety unit is again difficult for the same reasons as mentioned above in connection with the determination of the operating point of the control thermostat unit.
The system disclosed in the present application represents an improvement over the system described in U.S. Application Ser. No. 704,037, filed July 9, 1976; now U.S. Pat. No. 4,123,807 assigned to Aisin Seiki Kabushiki Kaisha, the assignee of the present application.